rpms: Use git version information

rpms: Use git version information

Use the git version information when building RPMS, rather than hard
coding it into configure.ac.

(cherry picked from commit 6a27e228bac196abada96f34ca9cd57f32e31f5c)
Reviewed-on: http://gerrit.openafs.org/4983
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Derrick Brashear <shadow@dementia.org>
Change-Id: Ibfe38e924eb53e279aaeff77882957a32ebb279b
Reviewed-on: http://gerrit.openafs.org/5008
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Derrick Brashear <shadow@dementia.org>